Method for assigning and processing a label in an optical network, optical communication device, and optical communication system

ABSTRACT

The present invention discloses a method for assigning and processing a label in an optical network. The method includes: learning that a label switched path is required to be established in an optical network; generating a label, in which the label is used for indicating that a first optical channel data unit is multiplexed to a second optical channel data unit; the label includes a tributary slot type indication field that is used for indicating a tributary slot type of the second optical channel data unit, and the label further includes a tributary slot assignment indication field that is used for indicating a tributary slot occupied in the second optical channel data unit into which the first optical channel data unit is multiplexed; and sending the label to a node on the label switched path by a signaling message of GMPLS.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 15/090,418, filed on Apr. 4, 2016, which is acontinuation application of U.S. patent application Ser. No. 14/616,345,filed on Feb. 6, 2015, now U.S. Pat. No. 9,307,303, which is acontinuation application of U.S. patent application Ser. No. 13/342,695,filed on Jan. 3, 2012, now U.S. Pat. No. 8,971,711, which is acontinuation of International Patent Application No. PCT/CN2010/074760,filed Jun. 30, 2010. The International Application claims priority toChinese Patent Application No. 200910150111.X, filed Jul. 3, 2009. Theafore-mentioned patent applications are hereby incorporated by referencein their entireties.

FIELD OF THE INVENTION

The present invention relates to the field of optical communicationtechnology, and in particular, to a method for assigning and processinga label in an optical network, an optical communication device, and anoptical communication system.

BACKGROUND OF THE INVENTION

The optical transport network (OTN, Optical Transport Network)technology is a new optical transport technology, which is capable ofimplementing flexible scheduling and management of high-capacityservices, and already becomes a mainstream technology of a backbonetransport network currently.

Three signal types are defined in the existing OTN: an optical channeldata unit 1 (ODU1, Optical Channel Data Unit 1), an ODU2, and an ODU3,which respectively include 1, 4, and 16 tributary slots, and the typesof the tributary slots are all 2.5 Gb/s. During the data transmission ofthe optical network, multiplexing or mapping relationships of relatedtransport units are involved, so that when a transmission path is beingestablished, it is required to designate how an ODUj is multiplexed toan ODUk (j<k), or how the ODUj is mapped to an optical channel transportunit OTUk (Optical Channel Transport Unit) (j=k). In the prior art, amethod for assigning labels for neighboring nodes is usually adopted todesignate the multiplexing or mapping relationships. An ODU label isdisclosed in the prior art, which mainly includes: a t1 field, a t2field, and a t3 field, so different signal types, for example, an ODU1signal, an ODU2 signal or an ODU3 signal, are denoted through differentvalues of the t1 field, the t2 field, and the t3 field, and a tributaryslot occupied during multiplexing is denoted.

During the research and implementation of the method, the inventors ofthe present invention find that:

Currently, new ODU signal types, such as an ODU0 suitable fortransporting low-rate signals, an ODU4 suitable for transport at ahigher rate, and an ODU2 e, an ODU3 e 1, an ODU3 e 2, and abandwidth-variable ODUflex, are proposed in the industry. In addition, anew tributary slot type with the bandwidth 1.25 Gb/s is furtherproposed. However, in the prior art, the label only supports the threesignal types: the ODU1, the ODU2, and the ODU3, and at the same timeonly supports a tributary slot type of 2.5 Gb/s. Also, the label in theprior art has poor expandability and is unable to support new signaltypes and tributary slot types by extension. Therefore, the prior art isunable to assign a label in an OTN network that supports new signaltypes and tributary slot types.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method for assigning andprocessing a label in an optical network, an optical communicationdevice, and an optical communication system, capable of assigning labelsfor an OTN network supporting different signal types and tributary slottypes.

An embodiment of the present invention provides a method for assigningand processing a label in an optical network, which includes:

-   -   learning that a label switched path is required to be        established in an optical network;    -   generating a label according to a signal type of the label        switched path and network resources, in which the label is used        for indicating that a first optical channel data unit is        multiplexed to a second optical channel data unit; the label        includes a tributary slot type indication field that is used for        indicating a tributary slot type of the second optical channel        data unit, and the label further includes a tributary slot        assignment indication field that is used for indicating a        tributary slot occupied in the second optical channel data unit        into which the first optical channel data unit is multiplexed;        and    -   sending the label to a node on the label switched path by a        signaling message of General Multi-Protocol Label Switching.

An embodiment of the present invention provides a method for assigningand processing a label in an optical network, which includes:

-   -   obtaining a label by a signaling message of General        Multi-Protocol Label Switching, in which the label is used for        indicating that a first optical channel data unit is multiplexed        to a second optical channel data unit; the label includes a        tributary slot type indication field that is used for indicating        a tributary slot type of the second optical channel data unit,        and the label further includes a tributary slot assignment        indication field that is used for indicating a tributary slot        occupied in the second optical channel data unit into which the        first optical channel data unit is multiplexed; and    -   multiplexing the first optical channel data unit to the second        optical channel data unit according to field information in the        label.

An embodiment of the present invention provides a method for assigningand processing a label in an optical network, which includes:

-   -   learning that a label switched path is required to be        established in an optical network;    -   generating a label according to a signal type of the label        switched path and network resources, in which the label is used        for indicating that an optical channel data unit is mapped to an        optical channel transport unit; the label includes a first        signal type indication field that is used for indicating a        signal type of the optical channel data unit; and the label        further includes a second signal type indication field that is        used for indicating a signal type of the optical channel        transport unit; and    -   sending the label to a node on the label switched path by a        signaling message of General Multi-Protocol Label Switching.

An embodiment of the present invention provides a method for assigningand processing a label in an optical network, which includes:

-   -   obtaining a label by a signaling message of General        Multi-Protocol Label Switching, in which the label is used for        indicating that an optical channel data unit is mapped to an        optical channel transport unit; the label includes a first        signal type indication field that is used for indicating a        signal type of the optical channel data unit; and the label        further includes a second signal type indication field that is        used for indicating a signal type of the optical channel        transport unit; and    -   mapping the first optical channel data unit to the second        optical channel data unit according to field information in the        label.

An embodiment of the present invention provides an optical communicationdevice, which includes:

-   -   a processing unit, configured to learn that a label switched        path is required to be established in an optical network; and        generate a label according to a signal type of the label        switched path and network resources, in which the label is used        for indicating that a first optical channel data unit is        multiplexed to a second optical channel data unit; the label        includes a tributary slot type indication field that is used for        indicating a tributary slot type of the second optical channel        data unit, and the label further includes a tributary slot        assignment indication field that is used for indicating a        tributary slot occupied in the second optical channel data unit        into which the first optical channel data unit is multiplexed;        and    -   a sending unit, configured to send the label to a node on the        label switched path by a signaling message of General        Multi-Protocol Label Switching.

An embodiment of the present invention provides an optical communicationdevice, which includes:

-   -   a processing unit, configured to learn that a label switched        path is required to be established in an optical network, and        generate a label according to a signal type of the label        switched path and network resources, in which the label is used        for indicating that an optical channel data unit is mapped to an        optical channel transport unit, the label includes a first        signal type indication field that is used for indicating a        signal type of the optical channel data unit; and the label        further includes a second signal type indication field that is        used for indicating a signal type of the optical channel        transport unit; and    -   a sending unit, configured to send the label to a node on the        label switched path by a signaling message of General        Multi-Protocol Label Switching.

An embodiment of the present invention provides an optical communicationdevice, which includes:

-   -   an obtaining unit, configured to obtain a label by a signaling        message of General Multi-Protocol Label Switching, in which the        label is used for indicating that a first optical channel data        unit is multiplexed to a second optical channel data unit; the        label includes a tributary slot type indication field that is        used for indicating a tributary slot type of the second optical        channel data unit, and the label further includes a tributary        slot assignment indication field that is used for indicating a        tributary slot occupied in the second optical channel data unit        into which the first optical channel data unit is multiplexed;        and    -   a multiplexing unit, configured to multiplex the first optical        channel data unit to the second optical channel data unit        according to field information in the label.

An embodiment of the present invention provides an optical communicationdevice, which includes:

-   -   an obtaining unit, configured to obtain a label by a signaling        message of General Multi-Protocol Label Switching, in which the        label is used for indicating that an optical channel data unit        is mapped to an optical channel transport unit; the label        includes a first signal type indication field that is used for        indicating a signal type of the optical channel data unit; and        the label further includes a second signal type indication field        that is used for indicating a signal type of the optical channel        transport unit; and    -   a mapping unit, configured to map the optical channel data unit        into the optical channel transport unit according to field        information in the label.

An embodiment of the present invention provides an optical communicationsystem, which includes:

-   -   a first optical communication device, configured to learn that a        label switched path is required to be established in an optical        network; generate a label according to a signal type of the        label switched path and network resources, in which the label is        used for indicating that a first optical channel data unit is        multiplexed to a second optical channel data unit; the label        includes a tributary slot type indication field that is used for        indicating a tributary slot type of the second optical channel        data unit, and the label further includes a tributary slot        assignment indication field that is used for indicating a        tributary slot occupied in the second optical channel data unit        into which the first optical channel data unit is multiplexed;        and send the label to a node on the label switched path by a        signaling message of General Multi-Protocol Label Switching; and    -   a second optical communication device, configured to obtain the        label by the signaling message of General Multi-Protocol Label        Switching sent by the first optical communication device, and        multiplex the first optical channel data unit to the second        optical channel data unit according to field information in the        label.

An embodiment of the present invention provides an optical communicationsystem, which includes:

-   -   a first optical communication device, configured to learn that a        label switched path is required to be established in an optical        network; generate a label according to a signal type of the        label switched path and network resources, in which the label is        used for indicating that an optical channel data unit is mapped        to an optical channel transport unit; the label includes a first        signal type indication field that is used for indicating a        signal type of the optical channel data unit, and the label        further includes a second signal type indication field that is        used for indicating a signal type of the optical channel        transport unit; and send the label to a node on the label        switched path by a signaling message of General Multi-Protocol        Label Switching; and    -   a second optical communication device, configured to obtain the        label by the signaling message of General Multi-Protocol Label        Switching sent by the first optical communication device, and        map the optical channel data unit into the optical channel        transport unit according to field information in the label.

It can be seen from the technical solutions that, the generated label inthe embodiments of the present invention is used for indicating that thefirst optical channel data unit is multiplexed to the second opticalchannel data unit, the label includes a tributary slot type indicationfield that is used for indicating a tributary slot type of the secondoptical channel data unit, and the label further includes a tributaryslot assignment indication field that is used for indicating a tributaryslot occupied in the second optical channel data unit into which thefirst optical channel data unit is multiplexed. In this way, both theoriginal and new signal types, and original and new tributary slot typescan be supported by the generated label in the embodiments of thepresent invention, and therefore labels may be assigned for an OTNnetwork supporting different signal types and tributary slot types.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method for assigning and processing a labelin an optical network according to Embodiment 1 of the presentinvention;

FIG. 2 is a flow chart of a method for assigning and processing a labelin an optical network according to Embodiment 2 of the presentinvention;

FIG. 3 is a schematic structural diagram of a label according to anembodiment of the present invention;

FIG. 4 is a schematic diagram of an example of a label according to anembodiment of the present invention;

FIG. 5 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 3 of the present invention;

FIG. 6 is a schematic diagram of a label 1 assigned in Embodiment 3;

FIG. 7 is a schematic diagram of a label 2 assigned in Embodiment 3;

FIG. 8 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 4 of the present invention;

FIG. 9 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 5 of the present invention;

FIG. 10 is a schematic diagram of a format of a Label ERO subobject of alabel according to Embodiment 5;

FIG. 11 is a schematic diagram of a structure 1 of an opticalcommunication device according to an embodiment of the presentinvention;

FIG. 12 is a schematic diagram of a structure 2 of an opticalcommunication device according to an embodiment of the presentinvention;

FIG. 13 is a schematic diagram of a structure 3 of an opticalcommunication device according to an embodiment of the presentinvention;

FIG. 14 is a schematic diagram of a structure 4 of an opticalcommunication device according to an embodiment of the presentinvention; and

FIG. 15 is a schematic structural diagram of an optical communicationsystem according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

An embodiment of the present invention provides a method for assigningand processing a label in an optical network, which is capable ofassigning labels for an OTN network supporting different signal typesand tributary slot types. An embodiment of the present invention furtherprovides a corresponding optical communication device and opticalcommunication system. The detailed illustrations are provided in thefollowing.

FIG. 1 is a flow chart of a method for assigning and processing a labelin an optical network according to Embodiment 1 of the presentinvention, which mainly includes the following steps:

Step 101: Learn that a label switched path is required to be establishedin an optical network.

Step 102: Generate a label according to a signal type of the labelswitched path and network resources, in which the label is used forindicating that a first optical channel data unit is multiplexed to asecond optical channel data unit, the label includes a tributary slottype indication field that is used for indicating a tributary slot typeof the second optical channel data unit, and the label further includesa tributary slot assignment indication field that is used for indicatinga tributary slot occupied in the second optical channel data unit intowhich the first optical channel data unit is multiplexed.

The tributary slot assignment indication field uses a set value at adifferent bit to indicate the tributary slot occupied in the firstoptical channel data unit into which the second optical channel dataunit is multiplexed.

Step 103: Send the label to a node on the label switched path by asignaling message of general multi-protocol label switching (GMPLS,General Multi-Protocol Label Switching).

It should be noted that the label further includes a first signal typeindication field that is used for indicating a signal type of the firstoptical channel data unit; and a second signal type indication fieldthat is used for indicating a signal type of the second optical channeldata unit.

The label further includes a length field that is used for indicating alength of the tributary slot assignment indication field.

The length of the tributary slot assignment indication field is equal tothe number of tributary slots of the second optical channel data unit.

In addition, when one label exists, the label is generated by one nodeon the label switched path; and the node sends the label to an upstreamneighboring node of the node or a downstream neighboring node of thenode on the label switched path by the signaling message.

Alternatively, when multiple labels exist, a label is generated by ahead node on the label switched path for each of multiple downstreamnodes of the head node on the label switched path; and the head nodesends the label to each of the multiple downstream nodes by thesignaling message.

It can be seen from the content of the embodiment that, the generatedlabel in the embodiment of the present invention is used for indicatingthat the first optical channel data unit is multiplexed to the secondoptical channel data unit, the label includes a tributary slot typeindication field that is used for indicating a tributary slot type ofthe second optical channel data unit, and the label further includes atributary slot assignment indication field that is used for indicating atributary slot occupied in the second optical channel data unit intowhich the first optical channel data unit is multiplexed. In this way,both the original and new signal types and the original and newtributary slot types can be supported by the generated label in theembodiments of the present invention, and therefore labels may beassigned for an OTN network supporting different signal types andtributary slot types.

FIG. 2 is a flow chart of a method for assigning and processing a labelin an optical network according to Embodiment 2 of the presentinvention, which mainly includes the following steps:

Step 201: Learn that a label switched path is required to be establishedin an optical network.

Step 202: Generate a label according to a signal type of the labelswitched path and network resources, in which the label is used forindicating that an optical channel data unit is mapped into an opticalchannel transport unit, the label includes a first signal typeindication field that is used for indicating a signal type of theoptical channel data unit; and the label further includes a secondsignal type indication field that is used for indicating a signal typeof the optical channel transport unit.

Step 203: Send the label to a node on the label switched path by asignaling message of General Multi-Protocol Label Switching, GMPLS.

It can be seen from the content of the embodiment that, the generatedlabel in the embodiments of the present invention is used for indicatingthat the optical channel data unit is mapped to the optical channeltransport unit, the label includes a first signal type indication fieldthat is used for indicating a signal type of the optical channel dataunit; second signal type indication field that is used for indicating asignal type of the optical channel transport unit. In this way, both theoriginal and new signal types and the original and new tributary slottypes can be supported by the generated label in the embodiments of thepresent invention, and therefore labels may be assigned for an OTNnetwork supporting different signal types and tributary slot types.

The embodiments of the present invention are illustrated in furtherdetail in the following.

The label disclosed in the embodiment of the present invention is firstintroduced.

FIG. 3 is a schematic structural diagram of a label according to anembodiment of the present invention.

For illustration, the label in FIG. 3 is used for indicating that afirst optical channel data unit is multiplexed to a second opticalchannel data unit. The first optical channel data unit is, for example,an ODUj (j=0, 1, 2, 3, 4, 2e, 3e1, 3e2, and flex), and the secondoptical channel data unit, is for example, an ODUk (k=1, 2, 3, and 4).

As shown in FIG. 3, an ODUj field, an ODUk field, a T field, and a bitmap Bit Map field are mainly included.

The T field is a tributary slot type indication field that is used forindicating a tributary slot type of a second optical channel data unit,for example, indicating a tributary slot type of the ODUk. The bit mapBit Map field is a tributary slot assignment indication field that isused for indicating a tributary slot occupied in the second opticalchannel data unit into which the first optical channel data unit ismultiplexed, for example, indicating a tributary slot occupied in theODUk into which the ODUj is multiplexed. The ODUj field is a firstsignal type indication field that is used for indicating a signal typeof the first optical channel data unit. The ODUk field is a secondsignal type indication field that is used for indicating a signal typeof the second optical channel data unit. The ODUj field and the ODUkfield (both can occupy 4 bits) denote that the ODUj is multiplexed tothe ODUk (j=0, 1, 2, 3, 4, 2e, 3e1, 3e2, and flex, k=1, 2, 3, and 4, andthe bandwidth of the ODUj is smaller than that of the ODUk).

It should be noted that if the label indicates that the optical channeldata unit is mapped to the optical channel transport unit, the labelincludes only the ODUj field and the OTUk field (both can occupy 4 bits,and j=k =1, 2, 3, and 4).

For example, the values of the related fields may be as shown in Table1:

TABLE 1 Signal Type Indicated By the Signal Type Indicated By the ValuesODUj ODUk or OTUk 0 ODU0 Reserved for use in future extension 1 ODU1ODU1 or OTU1 2 ODU2 ODU2 or OTU2 3 ODU3 ODU3 or OTU3 4 ODU4 ODU4 or OTU45 ODU2e Reserved for use in future extension 6 ODU3e1 Reserved for usein future extension 7 ODU3e2 Reserved for use in future extension 8ODUflex Reserved for use in future extension Others Reserved for use infuture Reserved for use in future extension extension

For example, ODUj=2, ODUk=4, which denote that the ODU2 is multiplexedto the ODU4; and ODUj=2, OTUk=2, which denote that the ODU2 is mapped tothe OTU2.

T (which can occupy 2 bits) denotes a tributary slot type. For example,T=0, which denotes that the tributary slot type is 1.25 Gb/s, and T=1,which denotes that the tributary slot type is 2.5 Gb/s.

The Bit Map denotes into which tributary slots of the ODUk the ODUj ismultiplexed. A length of the Bit Map is equal to the number of tributaryslots of the ODUk. When an nth bit of the Bit Map is filled with “1”, itdenotes that the ODUj is multiplexed to an nth tributary slot of theODUk. The total number of tributary slots of all ODU signals is shown inTable 2:

TABLE 2 Total Number of Time Total Number of Time ODU Signal Slots of1.25 Gb/s Slots of 2.5 Gb/s ODU1 2 1 ODU2 8 4 ODU3 32 16 ODU4 80 40

It should be noted that, theoretically, the ODU4 can be divided into 40tributary slots with the granularity of 2.5 Gb/s. However, the ODU4defined by the existing OTN standard does not support the division ofthe granularity of 2.5 Gb/s.

In addition, when the label indicates that the ODUj is mapped to theOTUk (j=k), the Bit Map is null because it is not required to specifywhich tributary slots are used.

One example of the label is introduced in the following. FIG. 4 is aschematic diagram of an example of a label according to an embodiment ofthe present invention.

As shown in FIG. 4, ODUj=1, ODUk=2, denoting that the label indicatesthat an ODU1 is multiplexed to an ODU2.

T=0, which denotes that the tributary slot type is 1.25 Gb/s, so theODU2 has 8 tributary slots in total, and the ODU1 needs to occupy 2tributary slots of the ODU2.

The first 1 bit and the fourth bit of the Bit Map are “1”, which denotesthat the ODU1 is multiplexed to the first tributary slot and the fourthtributary slot of the ODU2.

Reserved refers to a reserved field for use in future extension.

It should be noted that the label disclosed in the embodiment of thepresent invention may also not explicitly point out the ODUj field andthe ODUk field, that is because the node may also learn the signal typeof the ODUj according to a traffic parameter in the received signalingmessage. In addition, the label is related to a port, and the node maylearn a signal type of the ODUk through a port attribute. Therefore, thetwo fields are not mandatory, but when the ODUj field and the ODUk fieldare explicitly pointed out, the processing on the control plane becomesmore convenient. Moreover, the label may further adopt a Length field toexplicitly point out the length of the Bit Map.

In addition, when a low-rate ODUj is multiplexed to a high-rate ODUk,for example, the ODU0 or the ODU1 is multiplexed to the ODU4, becausethe number of tributary slots of the ODUk is large, and the number oftributary slots of the ODUk occupied by the ODUj is small, in this case,in the Bit Map field of the label, many bits with the value 0 exist, andat this time, a bit map compression method may be adopted to reduce thelength of the label. The specific compression method is that in thelabel format in FIG. 3, one bit is selected from the reserved (Reserved)field to denote whether the label adopts the bit map compression method(for example, when the bit is 1, it denotes that the bit map of thelabel is compressed, and 0 denotes that no compression occurs). In thecompressed part of the bit map, every 8 bits denote a specific positionof one tributary slot of an ODUk occupied by the ODUj, for example, whena value of a number formed of 8 bits is n, it denotes that the ODUjoccupies the nth tributary slot of the ODUk. If the ODUj needs to occupymultiple tributary slots of the ODUk, the compressed part of the bit mapincludes a plurality of 8 bits.

In addition, it should be noted that in the case of how the ODUj ismapped to the OTUk (j=k), the disclosed label may need to include onlythe ODUj field and the OTUk field (j=k), and does not need the T fieldand the Bit Map field.

The label disclosed in the embodiment of the present invention isintroduced in detail, and the method according to the embodiment of thepresent invention may be applied in an OTN network controlled by theGMPLS, so that in the following content, the processing process ofassigning a label according to an embodiment of the present invention isintroduced by taking the application scenario in which a label isassigned in a network to establish one label switched path (LSP, LabelSwitched Path) of the ODUj. The following embodiments mainly include amethod for assigning a label downstream, a method for assigning a labelupstream, and a method for globally and explicitly assigning a label,which respectively correspond to Embodiment 3 to Embodiment 5.

Embodiment 3

Embodiment 3 is about a method for assigning a label downstream, andassigning a label downstream is the most basic method for assigning alabel in the GMPLS. The method is mainly: starting sending a pathmessage (Path message) from a source node to a destination node hop byhop, requesting establishment of an LSP of a certain type; reserving, bythe destination node, according to network resources, resources andassigning a label, and sending a reservation (Resv, Reservation) messageto an upstream node, in which the message carries a label, and the labelindicates which resources are reserved specifically. Each intermediatenode repeats the foregoing actions till the source node.

An example is provided in the following. It is assumed that a linkbetween a node A and a node B is of an ODU2 type, and a link between thenode B and a node C is of an ODU3 type, and the tributary slot types areboth 1.25 Gb/s. The source node is the node A and the destination nodeis the node C. Now, a client layer requires a service layer to establisha path of an ODU1 type between the nodes A-C. It is assumed that thenode A already calculates a route (A-B-C), and the resource reservationprotocol-traffic engineering (RSVP-TE, Resource ReserVationProtocol-Traffic Engineering) extended from the GMPLS is adopted, andother protocols, for example, a label distribution protocol (LDP, LabelDistribution Protocol may also be adopted, and the process is similar).For the process of establishing the LSP, refer to FIG. 5.

FIG. 5 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 3 of the present invention,which mainly includes the following steps:

Step 501: The node A sends a Path message to the node B, in which themessage carries a traffic parameter designating that one LSP of the ODU1type needs to be established.

Step 502: The node B sends the Path message to the node C, in which themessage carries the traffic parameter designating that one LSP of theODU1 type needs to be established.

Step 503: The node C is a destination node, and according to thereceived Path message, learns that one LSP of the ODU1 type needs to beestablished, and therefore learns that a label needs to be assigned, andreserves resources for the LSP that needs to be established andgenerates a corresponding label.

The node C selects and reserves resources for an ingress port (adirection B-C). For example, because the node C finds that the first andfourth tributary slots on the link BC are currently free, the node Cselects and reserves the two tributary slots, and then generates andsaves a label L (B, C) in a direction of the ingress port. The format ofthe generated label is as shown in FIG. 6.

FIG. 6 is a schematic diagram of a label 1 assigned in Embodiment 3.

ODU =1, and ODUk=3, which denote that the ODU1 is multiplexed to theODU3, and T=0, which denotes that a tributary slot type is 1.25 Gb/s.Because the ODU3 has 32 tributary slots of the 1.25 Gb/s type, the BitMap has 32 bits, in which the first and fourth bits are 1, which denotesthat the node C has reserved the first and fourth tributary slots of theODU3, that is, the ODU1 is to be multiplexed to the first and fourthtributary slots of the ODU3.

Step 504: The node C sends a Resv message to the node B, in which themessage carries the generated label L (B, C).

Step 505: When receiving the Resv message, the node B reserves resourcesfor an LSP to be established and generates a corresponding label.

The node B performs the following operations:

-   -   (1) By analyzing the label L (B, C), resources (that is, the        first and fourth tributary slots in an egress port) of an egress        port of the node B to be used by the ODU1 service may be        learned. The node B records the label L (B, C) locally and        reserves the resources of the egress port for an ODU1 service.    -   (2) The node B selects and reserves the resources of the ingress        port (a direction A-B). For example, B finds that the second and        fourth tributary slots on the link AB are currently free, and        therefore selects and reserves the two tributary slots and then        generate a label L (A, B) in a direction of the ingress port.        The format of the generated label is as shown in FIG. 7.

FIG. 7 is a schematic diagram of a label 2 assigned in Embodiment 3.

ODUj=1, and ODUk=2, which denote that the ODU1 is multiplexed to theODU2, and T=0, which denotes that a tributary slot type is 1.25 Gb/s.Because the ODU2 has 8 tributary slots of the 1.25 Gb/s type, the BitMap has 8 bits, in which the second and fourth bits are 1, which denotesthat the node B has reserved the second and fourth tributary slots ofthe ODU2, that is, the ODU1 is to be multiplexed to the second andfourth tributary slots of the ODU2.

-   -   (3) A control plane of the node B delivers a command to a data        plane, and establishes a cross-connection from the ingress port        to the egress port.

It should be noted that the process is not a mandatory process, and insome special scenarios, the cross-connection may be not established. Forexample, when a shared recovery path is being established, it can bespecified that a label is assigned on a control plane only, and thecross-connection is established for the recovery path only when afailure occurs on a work path.

Step 506: The node B sends a Resv message to the node A, in which themessage carries the label L (A, B).

Step 507: When receiving the Resv message, the node A may learnresources (that is, the second and fourth tributary slots in the egressport) of an egress port of a node A to be used by the ODU1 service byanalyzing the label L (A, B). The node A records the label locally andreserves resources of the egress port for the ODU1 service.

Through the foregoing process, the LSP on the service layer issuccessfully established by using the assigned label. During the servicetransport, the node A may, according to the locally saved label L (A,B), multiplex the ODU1 to the second and fourth tributary slots of theODU2 and transport to the node B. The node B, according to the locallysaved label L (A, B) in the direction of the ingress port, receives theODU1 from the second and fourth tributary slots of the ODU2, andaccording to the locally saved label L (B, C) in the direction of theegress port, multiplexes the ODU1 to the first and fourth tributaryslots of the ODU3 and transports to the node C. The node C, according tothe locally saved label L (B, C) in the direction of the ingress port,and receives the ODU1 from the first and fourth tributary slots of theODU3, so as to implement the service transport process.

It can be seen that the generated label in the embodiments of thepresent invention includes an ODUj field, an ODUk field, a T field, anda bit map Bit Map field, and additionally the method for assigning alabel downstream is adopted. In this way, both the original and newsignal types and the original and new tributary slot types can besupported by the generated label in the embodiments of the presentinvention, and therefore labels may be assigned for an OTN networksupporting different signal types and tributary slot types.

Embodiment 4

Embodiment 4 is about a method for assigning a label upstream. In theGMPLS, it is further allowed that an upstream node assigns a label to adownstream node. The method is mainly: starting sending a Path messagefrom a source node to a downstream node hop by hop, requestingestablishment of an LSP, in which the message carries a label, and thelabel indicates which resources are specifically reserved. Thedownstream node judges whether the resources corresponding to the labelare available, and, if yes, continues to send the Path messagedownstream till the destination node.

An example is provided in the following. It is assumed that a linkbetween a node A and a node B is of an ODU2 type, a link between thenode B and a node C is of an ODU3 type, and the tributary slot type is1.25 Gb/s. Now, a client layer requires a service layer to establish apath of an ODU1 type between the node A and the node C. It is assumedthat the node A already calculates a route (A-B-C). For the process ofestablishing the LSP, refer to FIG. 8.

FIG. 8 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 4 of the present invention,which mainly includes the following steps:

Step 801: The node A reserves resources for an LSP to be established andgenerates a corresponding label.

The node A selects and reserves resources of an egress port (a directionA-B). For example, the node A finds that the second and fourth tributaryslots on the link AB are free, and therefore selects the two tributaryslots to carry the ODU1 service. The node A generates an upstream labelL (A, B) to indicate the resources assigned by the node A, and saves thelabel locally.

The content of the label generated by the node A is the same as that ofthe label generated by the node B in Embodiment 3. For details, refer tothe preceding description.

Step 802: The node A sends a Path message to the downstream node B, inwhich the message carries a traffic parameter (used for indicating thatan LSP of an ODU1 type needs to be established) and the label L (A, B).

Step 803: When receiving the Path message, the node B reserves resourcesfor the LSP to be established and generates a corresponding label.

The node B performs the following operations:

-   -   (1) The node B retrieves the upstream label L (A, B), and then        judges whether the resources on a corresponding ingress port        (that is, the second and fourth tributary slots of the ODU2        link) are available, and if available, records the label L        (A, B) locally.    -   (2) The node B selects and assigns resources of the egress port.        For example, the node B finds that the first and fourth        tributary slots on the link BC are free, and therefore selects        the two tributary slots to carry the ODU1 service. The node B        generates an upstream label L (B, C) to indicate resources        assigned by the node B, and saves the label locally.

The content of the label generated by the node B is the same as that ofthe label generated by the node in Embodiment 3. For details, refer tothe preceding description.

Step 804: The node B sends a Path message to the downstream node C, inwhich the message carries a traffic parameter (used for indicating thatan LSP of an ODU1 type needs to be established) and the label L (B, C).

Step 805: The node C is a destination node, and when receiving the Pathmessage, retrieves the upstream label L (B, C) from the message, andthen judges whether the resources on the ingress port (that is, thefirst and fourth tributary slots of the ODU3 link) are available. Ifavailable, the label is saved locally.

Step 806: The node C returns a Resv message to an upstream node B.

Step 807: When receiving the Resv message, the node B establishes across-connection from an ingress port to an egress port.

It should be noted that the process is not a mandatory process, and insome special scenarios, the cross-connection may be not established. Forexample, when a shared recovery path is being established, it may bespecified that a label is assigned on the control plane only, and thecross-connection is established for the recovery path only when afailure occurs on a work path.

Step 808: The node B sends a Resv message to the node A.

Through the foregoing process, the LSP on the service layer issuccessfully established by using the assigned label, which cantherefore be used for carrying the ODU1 service of the client layer. Fordetails, refer to the description in Embodiment 3.

It can be seen that the generated label in the embodiments of thepresent invention includes an ODUj field, an ODUk field, a T field, anda bit map Bit Map field, and additionally a method for assigning a labelupstream is adopted. In this way, both the original and new signal typesand the original and new tributary slot types can be supported by thegenerated label in the embodiments of the present invention, andtherefore labels may be assigned for an OTN network supporting differentsignal types and tributary slot types.

Embodiment 5

Embodiment 5 is mainly about an explicit label control method, which maydirectly specify what labels each node uses, that is, directly specifywhich tributary slots are used on each link to transport the ODUservice.

An example is provided in the following. It is assumed that a linkbetween a node A and a node B is of an ODU2 type, a link between thenode B and a node C is of an ODU3 type, and a tributary slot type is1.25 Gb/s. Now, the client layer requires the service layer to establishone path of an ODU1 type between A and C. It is assumed that the node Ahas already learned a route (A-B-C) of an LSP, and has learned that thesecond and fourth tributary slots of the ODU2 link between A and B areadopted, and the first and fourth tributary slots of the ODU3 linkbetween B and C are adopted. For the process of establishing the LSP,refer to FIG. 9.

FIG. 9 is a schematic diagram of a process of assigning a label toestablish an LSP according to Embodiment 5 of the present invention,which mainly includes the following steps:

Step 901: The node A confirms an explicit label, in which the explicitlabel includes labels generated by all nodes and reserved relatedresources.

The node A receives a path establishment command and determines explicitroute information and an explicit label. The information may be from anetwork manager or other network elements of the network side, and mayalso be obtained by the node A through automatic calculation.

The explicit route information is: the LSP to be established passesthrough the node A—the link AB—the node B—the link BC—the node C.

Explicit label information is: the label (L (A, B)) from the node A tothe node B, and the label (L (B, C)) from the node B to the node C. Thetwo labels have the same content as that in the two foregoingembodiments. For details, refer to the foregoing description.

In addition, the node A further saves an egress port label L (A, B) ofA.

Step 902: The node A sends a Path message to the downstream node B,which includes a traffic parameter, an EXPLICIT_ROUTE object (ERO,EXPLICIT_ROUTE object), a Label ERO subobject (Label ERO subobject), andan upstream label.

Multiple Label ERO subobjects may exist and one upstream label exists.

The EXPLICIT ROUTE object designates that the LSP to be establishedsubsequently passes through “the link AB—the node B—the link BC—the nodeC”, and no longer needs to indicate that “passing through the node A”.The Label ERO subobject designates the label (L (B, C)) from the node Bto the node C; and the upstream label designates the label (L (A, B))from the node A to the node B.

A format of a Label ERO subobject is as shown in FIG. 10.

FIG. 10 is a schematic diagram of a format of a Label ERO subobject of alabel in Embodiment 5.

A loose route identifier L field, a type Type field, a length Lengthfield, a service direction identifier U field, a label type C-Type fieldare the same as those in the prior art, and the label Label field adoptsthe label disclosed in the embodiment of the present invention.

Step 903: When receiving the Path message, the node B retrieves theupstream label L (A, B) from the message, and then judges whether theresources (the second and fourth tributary slots of the ODU2 link) on acorresponding ingress port are available, and if available, records thelabel L (A, B) locally.

In addition, the node B further saves the egress port label L (B, C) ofB.

Step 904: The node B sends a Path message to the downstream node C, inwhich the message carries a traffic parameter, an EXPLICIT_ROUTE object,and an upstream label.

The EXPLICIT_ROUTE object designates that the LSP to be establishedsubsequently passes through “link BC—the node C”; and the upstream labeldesignates the label (L (B, C)) from the node B to the node C. Thecontent of the label (L (B, C)) remains unchanged.

It should be noted that, because the node C is already the destinationnode at this time, the Label ERO subobject is null, and if the node C isnot the destination node, the Label ERO subobject is further included.

Step 905: The node C is a destination node. When receiving the Pathmessage, according to the upstream label L (B, C), the node C judgeswhether the resources on the ingress port (that is, the first and fourthtributary slots of the ODU3 link) are available. If available, the labelis locally stored.

Step 906: The node C returns a Resv message to the upstream node B.

Step 907: When receiving the Resv message, the node B establishes across-connection from the ingress port to the egress port.

It should be noted that the process is not a mandatory process.

Step 908: The node B sends a Resv message to the node A.

Through the foregoing process, the LSP of the service layer issuccessfully established by using the assigned label, which thereforecan be used for carrying the ODU1 service of the client layer. Fordetails, refer to the description in Embodiment 3.

It can be seen that the generated label in the embodiment of the presentinvention includes an ODUj field, an ODUk field, a T field, and a bitmap Bit Map field, and additionally, an explicit label control method isadopted. In this way, both the original and new signal types and theoriginal and new tributary slot types can be supported by the generatedlabel in the embodiments of the present invention, and therefore labelsmay be assigned for an OTN network supporting different signal types andtributary slot types.

It should be noted that in the foregoing, the case in which the ODUj ismultiplexed to the ODUk is used for illustration. For the process ofestablishing an LSP in the case that the ODUj is mapped to the OTUk(j=k), the principles are all similar, and only the formats of thegenerated labels are different.

The content in the foregoing is introduced the processing method ofassigning a label according to the embodiments of the present inventionin detail, and correspondingly, the embodiments of the present inventionprovide an optical communication device and an optical communicationsystem.

FIG. 11 is a schematic diagram of a structure 1 of an opticalcommunication device according to an embodiment of the presentinvention.

As shown in FIG. 11, the optical communication device includes: aprocessing unit 1101 and a sending unit 1102.

The processing unit 1101 is configured to learn that a label switchedpath is required to be established in an optical network; and generate alabel according to a signal type of the label switched path and networkresources, in which the label is used for indicating that a firstoptical channel data unit is multiplexed to a second optical channeldata unit, the label includes a tributary slot type indication fieldthat is used for indicating a tributary slot type of the second opticalchannel data unit, and the label further includes a tributary slotassignment indication field that is used for indicating a tributary slotoccupied in the second optical channel data unit into which the firstoptical channel data unit is multiplexed.

The sending unit 1102 is configured to send the label to a node on thelabel switched path by a signaling message of General Multi-ProtocolLabel Switching.

The processing unit 1101 includes an information learning subunit 11011and a label generation subunit 11012.

The information learning subunit 11011 is configured to learn that alabel switched path is required to be established in an optical network.

The label generation subunit 11012 is configured to generate a labelaccording to a signal type of the label switched path and networkresources, in which the label is used for indicating that a firstoptical channel data unit is multiplexed to a second optical channeldata unit; and the label includes: a tributary slot type indicationfield that is used for indicating a tributary slot type of the secondoptical channel data unit; a tributary slot assignment indication fieldthat is used for indicating a tributary slot occupied in the secondoptical channel data unit into which the first optical channel data unitis multiplexed; a first signal type indication field that is used forindicating a signal type of the first optical channel data unit; and asecond signal type indication field that is used for indicating a signaltype of the second optical channel data unit.

In addition, the label further includes a length field that is used forindicating a length of the tributary slot assignment indication field.The tributary slot assignment indication field uses a set value at adifferent bit to indicate the tributary slot occupied in the firstoptical channel data unit into which the second optical channel dataunit is multiplexed. A length of the tributary slot assignmentindication field is equal to the number of tributary slots of the secondoptical channel data unit.

When one label exists, the label is generated by the label generationsubunit 11012.

The sending unit 1102 sends the label to an upstream neighboring opticalcommunication device of the optical communication device or a downstreamneighboring optical communication device of the optical communicationdevice on the label switched path by the signaling message.

Alternatively, when multiple labels exist, a label is generated by thelabel generation subunit 11012 for each of multiple downstream opticalcommunication devices of the optical communication device on the labelswitched path.

The sending unit 1102 sends the label to each of the multiple downstreamoptical communication devices by the signaling message.

FIG. 12 is a schematic diagram of a structure 2 of an opticalcommunication device according to an embodiment of the presentinvention.

As shown in FIG. 12, the optical communication device includes: aprocessing unit 1202 and a sending unit 1203.

The processing unit 1202 is configured to learn that a label switchedpath is required to be established in an optical network; and generate alabel according to a signal type of the label switched path and networkresources, in which the label is used for indicating that an opticalchannel data unit is mapped to an optical channel transport unit, thelabel includes a first signal type indication field that is used forindicating a signal type of the optical channel data unit; and the labelfurther includes a second signal type indication field that is used forindicating a signal type of the optical channel transport unit.

The sending unit 1203 is configured to send the label to a node on thelabel switched path by a signaling message of General Multi-ProtocolLabel Switching.

FIG. 13 is a schematic diagram of a structure 3 of an opticalcommunication device according to an embodiment of the presentinvention.

As shown in FIG. 13, the optical communication device includes: anobtaining unit 1301 and a multiplexing unit 1302.

The obtaining unit 1301 is configured to obtain a label by a signalingmessage of General Multi-Protocol Label Switching, in which the label isused for indicating that a first optical channel data unit ismultiplexed to a second optical channel data unit, the label includes atributary slot type indication field that is used for indicating atributary slot type of the second optical channel data unit, and thelabel further includes a tributary slot assignment indication field thatis used for indicating a tributary slot occupied in the second opticalchannel data unit into which the first optical channel data unit ismultiplexed.

The multiplexing unit 1302 is configured to multiplex the first opticalchannel data unit to the second optical channel data unit according tofield information in the label.

The label obtained by the obtaining unit 1301 further includes a firstsignal type indication field that is used for indicating a signal typeof the first optical channel data unit; and a second signal typeindication field that is used for indicating a signal type of the secondoptical channel data unit.

FIG. 14 is a schematic diagram of a structure 4 of an opticalcommunication device according to an embodiment of the presentinvention.

As shown in FIG. 14, the optical communication device includes: anobtaining unit 1401 and a mapping unit 1402.

The obtaining unit 1401 is configured to obtain a label by a signalingmessage of General Multi-Protocol Label Switching, in which the label isused for indicating that an optical channel data unit is mapped to anoptical channel transport unit, the label includes a first signal typeindication field that is used for indicating a signal type of theoptical channel data unit; and the label further includes a secondsignal type indication field that is used for indicating a signal typeof the optical channel transport unit.

The mapping unit 1402 is configured to map the optical channel data unitinto the optical channel transport unit according to field informationin the label.

FIG. 15 is a schematic structural diagram of an optical communicationsystem according to an embodiment of the present invention.

As shown in FIG. 15, the optical communication system includes: a firstoptical communication device 1501 and a second optical communicationdevice 1502.

Implementation 1

The first optical communication device 1501 is configured to learn thata label switched path is required to be established in an opticalnetwork; generate a label according to a signal type of the labelswitched path and network resources, in which the label is used forindicating that a first optical channel data unit is multiplexed to asecond optical channel data unit; the label includes a tributary slottype indication field that is used for indicating a tributary slot typeof the second optical channel data unit, and the label further includesa tributary slot assignment indication field that is used for indicatinga tributary slot occupied in the second optical channel data unit intowhich the first optical channel data unit is multiplexed; and send thelabel to a node on the label switched path by a signaling message ofGeneral Multi-Protocol Label Switching.

The second optical communication device 1502 is configured to obtain thelabel by the signaling message of General Multi-Protocol Label Switchingsent by the first optical communication device 1501, and multiplex thefirst optical channel data unit to the second optical channel data unitaccording to field information in the label.

When one label exists, the label is generated by the first opticalcommunication device 1501.

The first optical communication device 1501 sends the label to anupstream neighboring optical communication device of the opticalcommunication device or a downstream neighboring optical communicationdevice of the optical communication device on the label switched path bythe signaling message.

Alternatively, when multiple labels exist, a label is generated by thefirst optical communication device 1501 for each of multiple downstreamoptical communication devices of the optical communication device on thelabel switched path.

The first optical communication device 1501 sends the label to each ofthe multiple downstream optical communication devices by the signalingmessage.

Implementation 2

The first optical communication device 1501 is configured to learn thata label switched path is required to be established in an opticalnetwork; generate a label according to a signal type of the labelswitched path and network resources, in which the label is used forindicating that an optical channel data unit is mapped to an opticalchannel transport unit, the label includes a first signal typeindication field that is used for indicating a signal type of theoptical channel data unit, and the label further includes a secondsignal type indication field that is used for indicating a signal typeof the optical channel transport unit; and send the label to a node onthe label switched path by a signaling message of General Multi-ProtocolLabel Switching.

The second optical communication device 1502 is configured to obtain thelabel by the signaling message of General Multi-Protocol Label Switchingsent by the first optical communication device 1501, and map the opticalchannel data unit into the optical channel transport unit according tofield information in the label.

In conclusion, the generated label in the embodiments of the presentinvention is used for indicating that the first optical channel dataunit is multiplexed to the second optical channel data unit, the labelincludes a tributary slot type indication field that is used forindicating a tributary slot type of the second optical channel dataunit, and the label further includes a tributary slot assignmentindication field that is used for indicating a tributary slot occupiedin the second optical channel data unit into which the first opticalchannel data unit is multiplexed. In this way, both the original and newsignal types and the original and new tributary slot types can besupported by the generated label in the embodiments of the presentinvention, and therefore labels may be assigned for an OTN networksupporting different signal types and tributary slot types.

It should be noted that the content such as information interaction andexecution among the units of the device and the system is based on thesame concept of the method embodiments of the present invention, so thatthe specific content may be referred to the illustration of the methodembodiments of the present invention, the description of which are nolonger provided here.

Those skilled in the art should understand that all or a part of thesteps of the method according to the embodiments may be implemented by aprogram instructing relevant hardware. The program may be stored in acomputer readable storage medium. The storage medium may include a ReadOnly Memory (ROM, Read Only Memory), a Random Access Memory (RAM, RandomAccess Memory), a magnetic disk or an optical disk.

The method for assigning and processing a label in an optical network,the optical communication device, and the optical communication systemaccording to the embodiments of the present invention are introduced indetail in the foregoing. The principle and implementation of the presentinvention are described herein through specific examples. Thedescription about the embodiments of the present invention is merelyprovided for ease of understanding of the method and core ideas of thepresent invention. Persons skilled in the art can make variations to thepresent invention in terms of the specific implementations andapplication scopes according to the ideas of the present invention.Therefore, the specification shall not be construed as a limit to thepresent invention.

What is claimed is:
 1. A method for sending a label in an opticalnetwork, comprising: generating a label indicating that a first opticalchannel data unit (ODU) is multiplexed to a second ODU; wherein thelabel comprises a tributary slot assignment indication field that isused for indicating a tributary slot occupied in the second ODU intowhich the first ODU is multiplexed; and sending the label.
 2. The methodaccording to claim 1, wherein: the label further comprises a lengthfield that is used for indicating a length of the tributary slotassignment indication field.
 3. The method according to claim 2, whereinthe length of the tributary slot assignment indication field is equal tothe number of a tributary slot of the second ODU.
 4. The methodaccording to claim 1, wherein the label further comprises a tributaryslot type indication field indicating a tributary slot type of thesecond ODU.
 5. The method according to claim 1, wherein: a signal typeof the first ODU is indicated by a traffic parameter, and/or a signaltype of the second ODU is indicated by a port attribute.
 6. The methodaccording to claim 1, wherein: the tributary slot assignment indicationfield uses a set value at a different bit to indicate the tributary slotoccupied in the second ODU unit into which the first ODU is multiplexed.7. The method according to claim 1, wherein: the first ODU is an ODUj,and the second ODU is an ODUk, wherein j is smaller than k.
 8. Themethod according to claim 1, wherein the generating a label comprises:generating, by a node, the label according to a network resource and asignal type of a label switched path to be established.
 9. A method forprocessing a label in an optical network, comprising: obtaining a labelindicating that a first optical channel data unit (ODU) is multiplexedto a second ODU; wherein the label comprises a tributary slot assignmentindication field that is used for indicating a tributary slot occupiedin the second ODU into which the first ODU is multiplexed; andmultiplexing the first ODU to the second ODU.
 10. The method accordingto claim 9, wherein: the label further comprises a length field that isused for indicating a length of the tributary slot assignment indicationfield.
 11. The method according to claim 10, wherein: the length of thetributary slot assignment indication field is equal to the number of atributary slot of the second ODU.
 12. The method according to claim 9,wherein: the tributary slot assignment indication field uses a set valueat a different bit to indicate the tributary slot occupied in the secondODU into which the first ODU is multiplexed.
 13. The method according toclaim 9, wherein: a signal type of the first ODU is indicated by atraffic parameter, and/or a signal type of the second ODU is indicatedby a port attribute.
 14. An apparatus in an optical network, theapparatus comprising: a processor and a computer readable medium havinga plurality of computer executable instructions stored thereon which,when executed by the processor, cause the processor to: generate a labelindicating that a first optical channel data unit (ODU) is multiplexedto a second ODU; wherein the label comprises a tributary slot assignmentindication field that is used for indicating a tributary slot occupiedin the second ODU into which the first ODU is multiplexed; and send thelabel.
 15. The apparatus according to claim 14, wherein: the labelfurther comprises a length field that is used for indicating a length ofthe tributary slot assignment indication field.
 16. The apparatusaccording to claim 15, wherein the length of the tributary slotassignment indication field is equal to the number of a tributary slotof the second ODU.
 17. The apparatus according to claim 14, wherein thelabel further comprises a tributary slot type indication fieldindicating a tributary slot type of the second ODU.
 18. An apparatus inan optical network, the apparatus comprising: a processor and a computerreadable medium having a plurality of computer executable instructionsstored thereon which, when executed by the processor, cause theprocessor to: obtain a label indicating that a first optical channeldata unit (ODU) is multiplexed to a second ODU; wherein the labelcomprises a tributary slot assignment indication field that is used forindicating a tributary slot occupied in the second ODU into which thefirst ODU is multiplexed; and multiplex the first ODU to the second ODU.19. The apparatus according to claim 18, wherein: the label furthercomprises a length field that is used for indicating a length of thetributary slot assignment indication field.
 20. The apparatus accordingto claim 19, wherein: the length of the tributary slot assignmentindication field is equal to the number of a tributary slot of thesecond ODU.